not enough umf in my pump

[smolo1]

Brand new post-er, hope i'm in the correct Forum. I have a Hardy H2, pushing water to a heat exchanger in my attic, then down to the basement to a 20-Plate heat exchanger next to my hot water heater. Need to push water back up to the attic before heading back to the stove. Grunfos pump at the stove can't push it all the way around the loop. Is it ok for me to add a second pump downstairs, inline with the existing system? Using 1" PEX all the way. Thanks!

 

[maple1]

How long is your pipe? Elevation difference between stove & system high/low points? Model of pump?

Are you sure you got all the air out?

 

[stee6043]

What's it doing that makes you think your pump isn't up for the job?

Depending on your heat load and distance of run that 1" pex may be more problematic than your pump size. That may not be a lot of flow for a long run, elevation change and two heat exchangers. Hopefully it's at least a quality insulated pex?

 

[Bob Rohr]

As noted above, generally the piping on those outdoor units is undersized for the load, sometimes grossly depending on the overall length of the circuit.

You have two choices, first determine the actual pumping requirement, tube, HX fittings,valves, everything in that loop.

If the tube is too small and cannot be easily upgraded then you need to throw more pump at it. Either a higher head pump, or two in series. Pumps in series double the head, gpm stays the same. Usually they are just bolted against one another for series pumping.

Just know that when you try to shove too much flow through and undersized circuit and you upsize pump you will increase the fluid velocity, and that can cause noise and wear issues in the components.

The tubing manufactures have graphs and tables to show you maximum flow rates and the pressure drop tables.

 

[Buzz Saw]

Could you do a primary/secondary loop instead of one long run?

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[StihlKicking]

Brand new post-er, hope i'm in the correct Forum. I have a Hardy H2, pushing water to a heat exchanger in my attic, then down to the basement to a 20-Plate heat exchanger next to my hot water heater. Need to push water back up to the attic before heading back to the stove. Grunfos pump at the stove can't push it all the way around the loop. Is it ok for me to add a second pump downstairs, inline with the existing system? Using 1" PEX all the way. Thanks!

Out of curiosity, if you have a H2 why use a plate exchanger at all? Why not use the copper loop inside the water jacket for DHW as designed. Then your pump would only need to feed the loop going to your HX.


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[hondaracer2oo4]

So first off I think you need to rethink your whole plumbing situation. I assume you have a back up heating system in the house??? How is this all tied togeather?

You would do yourself good to read the taco TD-10 on how to size your pump correctly. Just google TD-10 taco. This will help you understand how your system works and how to size your circ correctly.

Just off hand a few points. After the water goes up as long as the pump can push it up the vertical it is going to gain that same head on the way back down essentially balancing the head loss out so it's just a wash.

Why do you think your pump is to small?

That copper coil in the hardys is DUMB imo. Why would someone want to run a second set of insulated lines out to the boiler and add a second pump to the system for this? It makes zero sense. A flat plate hx or side arm on the water heater fed by the line feeding the house is the only reasonable way to go.

 

[StihlKicking]

So first off I think you need to rethink your whole plumbing situation. I assume you have a back up heating system in the house??? How is this all tied togeather?

You would do yourself good to read the taco TD-10 on how to size your pump correctly. Just google TD-10 taco. This will help you understand how your system works and how to size your circ correctly.

Just off hand a few points. After the water goes up as long as the pump can push it up the vertical it is going to gain that same head on the way back down essentially balancing the head loss out so it's just a wash.

Why do you think your pump is to small?

That copper coil in the hardys is DUMB imo. Why would someone want to run a second set of insulated lines out to the boiler and add a second pump to the system for this? It makes zero sense. A flat plate hx or side arm on the water heater fed by the line feeding the house is the only reasonable way to go.

Using the coil inside the H2 doesn’t require a second pump. One pump feeds the loop going to your Heat exchanger. You only need additional pumps for additional heat zones. Most H2 owners should have a cold water line running to their heater for the auto fill function, all you have to do is run one DHW line back and t into your homes DHW loop somewhere. That way whenever you turn a hot water tap on the natural line pressure moves cold water through the coil and hot water into the house. No pump required, no need for calculations. When using my H2 I actually bypass the water heater and now only use it for back up.


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[smolo1]

Thanks for the great thoughts and ideas. As usual, the simplest fix was the answer. Once I purged the system of ALL air, circulation was complete. I had to connect a garden hose fitting to the Pex in the basement and turn the hose all the way up with the system open - after a few minutes the air was gone. BTW - my H2 has had the copper coil and connections removed.